E 1294 – 89 (Reapproved 1999) Designation E 1294 – 89 (Reapproved 1999) Standard Test Method for Pore Size Characteristics of Membrane Filters Using Automated Liquid Porosimeter1 This standard is issu[.]
Trang 1Designation: E 1294 – 89 (Reapproved 1999)
Standard Test Method for
Pore Size Characteristics of Membrane Filters Using
This standard is issued under the fixed designation E 1294; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1 Scope
1.1 This test method describes a procedure for measuring
the pore size characteristics of membrane filters in the range of
approximately 0.05 to 300 µm
1.2 This test method uses the automated bubble point
method described in ASTM Test Method F 316
1.3 The liquid displacement technique used in this test
method depends upon the capillary rise created by surface
tension and uses the Washburn equation for calculating the
pore diameter
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use It is the
responsibility of the user of this standard to establish
appro-priate safety and health practices and determine the
applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 ASTM Standards:
F 316 Test Method for Pore Size Characteristics of
Mem-brane Filters for Use with Aerospace Fluids2
3 Summary of Test Method
3.1 A filter wet with liquid exhibits properties similar to
those of array of liquid filled capillaries (see Note) The sample
under test is thoroughly wetted with liquid of low surface
tension and low vapor pressure and placed in a sample holder
assembly An increasing air pressure is applied upstream of the
sample and as successively smaller pores empty, the air flow
across the sample is recorded as a function of applied pressure
The point of first flow is identified as the bubble point
(maximum pore size) This continues until the smallest
detect-able pore is reached This information is then compared with
the flow rate against applied pressure response for the dry
sample The pore size distribution is then obtained from wet
and dry curves
N OTE 1—This test method will not change the priorities of the
membrane if the test liquids are chosen to be compatible with the material
from which it is made.
4 Significance and Use
4.1 This test method may be used to determine the maxi-mum pore size, minimaxi-mum pore size, and mean flow pore size 4.2 The pore size distributions by flow, number, and volume can be deduced from pressure versus flow data
5 Apparatus
5.1 Source of Compressed Air up to 150 psi.
5.2 Automated Liquid Porosimeter.3
5.3 Sample Holders.
5.4 Metal Punch, used to cut a suitable size membrane filter
from the test sheet to fit the test filter holder
6 Reagents and Materials
6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society where such specifications are available.4Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination
6.2 Porofil.5
6.3 Isopropyl Alcohol.
6.4 Water.
6.5 Mineral Oil.
7 Procedure
7.1 Follow the manufacturer’s operating instructions to prepare the sample to introduce to the instrument for analysis 7.2 Establish standard sampling procedures to obtain repeat-able results
8 Operating Instructions
8.1 Operating instructions shall be supplied by the manu-facturer with every instrument The instructions shall contain:
1
This test method is under the jurisdiction of ASTM Committee E-48 on
Biotechnology and is the direct responsibility of Subcommittee E48.03 on Unit
Processes and Their Control.
Current edition approved March 31, 1989 Published May 1989.
2
Annual Book of ASTM Standards, Vol 11.01.
3 Coulter Porometer available from Coulter Electronics, Inc., 601 W 20th Street, Hialeah, Florida 33010 U.S.A., has been found suitable for this purpose.
4“Reagent Chemicals, American Chemical Society Specifications,’’ American Chemical Society, Washington DC For suggestions on the testing of reagents no
listed by the American Chemical Society, see“ Analar Standards for Laboratory U.K Chemicals,” BDH Ltd., Poole, Dorset, and the “United States Pharmacopeia.”
5 Porofil wetting liquid, available from Coulter Electronics, Inc., has been found suitable for this purpose.
1
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
Trang 28.1.1 Brief instructions of the operating principles of the
instrument,
8.1.2 Description of various systems,
8.1.3 Pore size range limitations,
8.1.4 Suggested maintenance procedures, and
8.1.5 Recommended spare parts
9 Verification
9.1 Verification of the performance of the instrument
func-tion may be determined by using well characterized
track-etched polycarbonate membrane filters6within the range of the
instrument
9.2 Interlaboratory comparisons within a particular industry
should be made using these well characterized membranes
10 Report
10.1 Report the following information:
10.1.1 Graph of raw data showing the pressure versus
percent flow
10.1.2 Tabulation of the raw data as well as the computed
differential percent flow, cumulative percent flow, differential
number percent, and cumulative number percent
10.1.3 Graphs of differential and cumulative flow as well as
number distributions plotted as pore size versus percent flow or
percent number
11 Precision and Bias
11.1 The precision of pore size analysis technique is not easy to verify The mathematical model chosen to relate applied pressure to pore size is that of a right cylindrical pore The best way to evaluate the precision is to evaluate the results from a series of track-etched polycarbonate membranes.6The manufacturer sizes them by electron microscopy, and uses ASTM porosimetry and bubble point tests to validate actual pore sizes
11.2 Precision—The reproducibility of each instrument can
be determined by repeatedly analyzing 0.1- and 10.0- µm polycarbonate membrane filters and determining the coefficient
of variation The results should not differ from the mean by more than the following amounts:
Pore Size Range
Repeatability: (same operator and apparatus), %
Reproducibility: (dif-ferent operators and apparatus), %
Since the change in pore size per unit change in applied pressure is greatest at large pore sizes and diminished hyper-bolically, repeatability and reproducibility increase accordingly with applied pressure
11.3 Bias—The bias between two different instruments can
be determined by comparing the mean flow pore sizes
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6 Polycarbonate membrane filters, available from Nucleopore Corp., 7035
Commerce Circle, Pleasanton, CA 94566, have been found suitable for this purpose.
E 1294
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